The present invention relates to ink sheet and polymer layer transfer sheet used in thermal transfer printing using recording medium such as thermal head laser and other optical head, energizing head, etc. The ink sheet relates to an ink sheet for sublimation type thermal transfer recording and/or an ink sheet for molten type thermal transfer recording, and the polymer layer transfer sheet relates to a polymer layer transfer sheet for sublimation type thermal transfer recording and/or an ink sheet for molten type thermal transfer recording.
In sublimation type or molten type thermal transfer recording, a film of polyethylene terephthalate (PET) is generally used as the base material for the ink sheet, but since the heat resistance and running lubricity of the PET film are insufficient when used in the recording head such as thermal head, a heat resistant lubricating layer having heat resistance and lubricity is usually formed and used at the base material side of the ink sheet in contact with the recording head.
As such heat resistant lubricating layer, it has been widely proposed to use substances, for example, a reaction-cures cured product of thermoplastic resin having alcoholic OH group and isocyanate compound as disclosed in Japanese Laid-open Patent No. 58-187396, stick-prevent layer made of silicone graft polymer as disclosed in Japanese Laid-open Patent No. 1-214475, a heat resistant protective layer of amino denatured polysiloxane and polyisocyanate or reaction product of both as disclosed in Japanese Laid-open Patent No. 5-131770, a vinyl polymer by block or graft coupling of organopolysiloxane units as disclosed in Japanese Laid-open Patent No. 61-143195, silicone denatured urethane resin as disclosed in Japanese Laid-open Patent No. 62-82086, and a heat resistant protective layer of thermoplastic resin and denatured silicone oil as disclosed in Japanese Laid-open Patent No. 6-316172.
The hitherto proposed heat resistant lubricating layer formed of resin having OH group and isocyanate is provided with heat resistance by forming a hardened matter, but in order to obtain running lubricity for the thermal head, it is required to add silicone substance such as silicone oil or lubricant such as wax. However, the hardened matter formed of resin having OH group and isocyanate is not so high in hardness as compared with, for example, a hardened matter obtained from epoxy acrylate known as so-called hard coating agent and reaction initiator, and therefore if the lubricant is added by the quantity necessary for obtaining running lubricity, thin lines may be formed in the recorded image.
This is because, when the heat resistant lubricating layer is formed by adding a lubricant to a hardened matter not so high in hardness, the substance favorably used as the lubricant is considerably low in molecular weight as compared with the resin forming the hardened matter, and therefore the heat resistance of the entire heating resistant lubricating layer is further lowered by addition of such lubricant of low molecular weight, or the film strength of the portion containing the lubricant is further lowered by addition of the lubricant, or the silicone derivative lubricant or fluorine derivative lubricant is large in surface dominant power and the hardening of the surface of the heat resistant lubricating layer is insufficient when existing dominantly on the surface of the heat resistant lubricating layer, and hence when running on the thermal head, fine running flaws are formed on the surface of the heat resistant lubricating layer and appear as thin lines in the recorded image.
When the heat resistant lubricating layer is made from the hitherto proposed silicone graft polymer, by grafting the silicone, the intrinsic film forming capability of the resin itself is relatively lowered, and the resin is likely to be scraped off by the thermal head, and the scraped resin contaminates the head, finally causing drop-out in the recorded image. Although the silicone graft polymer has lubricity because the silicone is grafted, the silicone content is small and it is still insufficient for obtaining a necessary running lubricity for the thermal head.
In the case of the heat resistant lubricating layer made from the hitherto proposed thermoplastic resin, denatured silicone oil, etc., when the ink sheet is wound and stored in the condition of high temperature and high humidity, since the heat resistance of the thermoplastic resin is not sufficient, fusion may occur between the color material layer and the heat resistant lubricating layer, or the running lubricity may be lowered after storage.
In a known method of forming a transfer image indirectly on an image receiving material such as plain paper, using an ink sheet having a color material, a resin layer transfer sheet having a resin layer, and an image receiving material, first the ink sheet and resin layer transfer sheet are laminated, the ink sheet is heated corresponding to the image signal applied from a thermal head, at least the color material of the ink sheet is transferred from the ink sheet to the resin layer of the resin layer transfer sheet to form an image on the resin layer transfer sheet, next the resin layer transfer sheet and image receiving material are laminated, and the resin layer forming the image on the resin layer transfer sheet is further thermally transferred to the image receiving material by heating means such as heat roll or thermal head, and finally the image is formed on the image receiving material.
In a method differing in the procedure of this recording process, first the resin layer transfer sheet and image receiving material are laminated, the resin layer on the resin layer transfer sheet is thermally transferred to the image receiving material by heating means such as heat roll or thermal head to form the resin layer on the image receiving material, next the image receiving material forming the resin layer and the ink sheet having a color material are laminated, and by heating the thermal head depending on the image similar same as above, at least the color material of the ink sheet is transferred to the resin layer of the image receiving material, and finally in image is formed on the image receiving material (for example, Japanese Laid-open Patent No. 60-222267).
Or, in order to protect the recorded image on the image receiving material, it is known to transfer the resin layer on the image on the image receiving material, and coat at least one side of the image receiving material.
As the heating means for thermal transfer of the resin layer on the resin layer transfer sheet to the image receiving material, when the heat roll is used, there is no problem, but a new problem occurs when the thermal head is used. That is, in the case of the heat roll, when the laminated resin layer transfer sheet and image receiving material are passed through between two rolls under pressure at least one of which is a heat roll (heater incorporated roll), since both rolls are rotating rolls, it is easy to pass between the rolls, but in the case of the thermal head consisting of the thermal head and platen roll under pressure, since one of them, that is, the thermal head is a non-rotating element, the resin layer transfer sheet running at the thermal head side cannot run stably. That is, no resin layer transfer sheet has been ever known to be sufficient in running lubricity and heat resistance against the heat generation of the thermal head at the time of transfer of resin layer of resin layer transfer sheet to the image receiving material, and capable of running stably without forming running flaws on the resin layer transferred to the image receiving material when the resin layer transfer sheet runs on the thermal head.
The medium for thermal transfer recording of the invention comprises:
(a) a base material having a first surface and a second surface,
(b) a transfer medium layer placed on the first surface side, and
(c) a heat resistant lubricating layer placed at the second surface side,
xe2x80x83in which the heat resistant lubricating layer is composed of:
(1) a resin containing a hydroxyl group,
(2) a crosslinking agent, and
(3) a thermoplastic resin.
The heat resistant lubricating layer has a crosslinked structure formed by crosslinking reaction between the crosslinking agent and the resin containing a hydroxyl group. The thermoplastic resin having at least one of thermal deformation temperature and glass transition temperature of 70xc2x0 C. or more is preferably used. The heat resistant lubricating layer can contain an adhesive. The medium for thermal transfer recording is an ink sheet for thermal transfer recording, and the color material layer has at least one of a dye which can be sublimated and transferred, a dye which can be diffused and transferred, and a color material that can be transferred with binder by heat. The medium for thermal transfer recording is a resin layer transfer sheet for thermal transfer recording, and the transfer medium layer has a resin layer. The resin layer having a property capable of containg a color material transferred by thermal transfer is preferably used.
The method of thermal transfer recording of the invention comprises:
(a) a step of feeding an ink sheet comprising a first base material, a color material layer placed at a first surface side of the first base material, and a first heat resistant lubricating layer placed at a second surface side of the first base material,
(b) a step of feeding a transfer sheet comprising a second base material, a resin layer placed at a third surface side of the second base material, and a second heat resistant lubricating layer placed at a fourth surface side of the second base material, and
(c) a step of transferring a record pattern by the color material contained in the color material layer to the resin layer side of the transfer sheet, by applying heat to the color material layer.
A manufacturing method of at least one layer of the first heat resistant lubricating layer and the second heat resistant lubricating layer comprises:
(1) a step of preparing a paint comprising a resin containing a hydroxyl group, a crosslinking agent to be crosslinked with the resin containing a hydroxyl group, and a thermoplastic resin having at least one of thermal deformation temperature and glass transition temperature of 70xc2x0 C. or more,
(2) a step of applying the paint at least to one side of at least one base material of the first base material and second base material, and
(3) a step of forming a heat resistant lubricating layer having a crosslink structure by crosslinking between the crosslinking agent contained in the paint and the resin containing a hydroxyl group.
The paint can contain an adhesive.
Preferably, the method of thermal transfer recording of the invention further comprises (d) a step of transferring the record pattern adhered to the transfer sheet to an image receiving material.
In this constitution, occurrence of thin line and dropout in recorded image can be prevented. Moreover, the running stability between the recording head and the color material layer is improved. In addition, when transferring the image transferred on the resin layer to the image receiving material, it is free from effects of heat generation from the thermal head or the like, and the running stability is enhanced and heat resistance is improved. Further, after storage in the atmosphere of high temperature and high humidity, deterioration of lubricating characteristic can be prevented.
It is hence an object of the present invention to obtain an ink sheet for thermal transfer recording not causing fine line or dropout in recorded image, excellent in running stability with the recording head owing to sufficient lubricating characteristic, free from fusion between the color material layer and the heat resistant lubricating layer after winding or storing in the condition of high temperature and high humidity, and having a heat resistant lubricating layer small in lowering of lubricating characteristic and excellent in storage characteristic, and a resin layer transfer sheet having a sufficient running lubricity and heat resistance against heat generation of the thermal head when transferring the resin layer of resin layer transfer sheet or the like onto the image receiving material, and capable of running stably without causing running flaw or the like when running in the resin layer or the like transferred onto the image receiving material when the resin layer transfer sheet runs on the thermal head.
The ink sheet of the present invention has a color material layer at one side of a base material, a heat resistant lubricating layer composed of a resin containing a hydroxyl group, a thermoplastic resin, an adhesive, a lubricant, and a crosslinking agent is formed at other side of the base material, the thermal deformation temperature or glass transition temperature of the thermoplastic resin is 70xc2x0 C. or more, and in the heat resistant lubricating layer, the resin containing a hydroxyl group forms a crosslink structure by reaction with the crosslinking agent.
Alternatively, a color material layer is formed at one side of a base material, a heat resistant lubricating layer composed of a resin containing a hydroxyl group, a thermoplastic resin, a lubricant, and a crosslinking agent is formed at other side of the base material, in the heat resistant lubricating layer, the resin containing a hydroxyl group forms a crosslink structure by reaction with the crosslinking agent, and the thermoplastic resin has the thermal deformation temperature or glass transition temperature of 70xc2x0 C. or more, and contains a hydroxyl group.
The image receiving layer transfer sheet of the present invention has a resin layer at one side of a base material, a heat resistant lubricating layer composed of a resin containing a hydroxyl group, a thermoplastic resin, an adhesive, a lubricant, and a crosslinking agent is formed at other side of the base material, and in the heat resistant lubricating layer, the resin containing a hydroxyl group forms a crosslink structure by reaction with the crosslinking agent.
Alternatively, a color material layer is formed at one side of a base material, a heat resistant lubricating layer composed of a resin containing a hydroxyl group, a thermoplastic resin, a lubricant, and a crosslinking agent is formed at other side of the base material, in the heat resistant lubricating layer, the resin containing a hydroxyl group forms a crosslink structure by reaction with the crosslinking agent, and the thermoplastic resin has the thermal deformation temperature or glass transition temperature of 70xc2x0 C. or more, and contains a hydroxyl group.